Abstract

Background and aims: Despite improvements in cardiovascular health and wellbeing, fear of exercise-induced hypoglycaemia and a paucity of evidence-based advice on how to manage diabetes during / after exercise remain significant barriers to exercise participation to people with Type 1 diabetes (T1DM). How professional athletes with T1DM manage their diabetes may provide an insight into optimising diabetes control around exercise. The present study examined glucose control in elite and recreational cyclists with and without T1DM during participation in the 2014 mHealth grand tour cycle ride from Brussels to Barcelona (EASD).

Materials and methods: Interstitial glucose (IG) concentrations were captured using continuous glucose monitoring (Dexcom G4®, INC, CA, USA) over a period of six consecutive days during a long-distance, multi-stage endurance cycling event in three groups of individuals: 10 recreationally-active type 1 diabetes individuals (T1rec), 8 elite cyclists with T1DM (T1pro), and 10 recreationally-active individuals without diabetes (CON). Each individual completed all 6 days of road cycling in full, covering a total distance of 1044km (174km av/day). Data (mean±SD) were analysed using a one-way ANOVA and independent student t tests.

Results: There was no change in glycaemic control over the course of the six days in any group, with similar mean, mean peak and mean nadir IG during ride time, daytime and night time periods (p>0.05). During the ride, mean IG was significantly greater in T1rec and significantly lower in T1pro compared to CON (7.6±2.8 vs. 5.2±2.7 vs. 6.3±01.0 mmol.l-1; p<0.05). During the ride, time spent in hypo- and hyperglycaemia were similar between T1rec and T1pro (hypo: 209±49 vs. 207±57min; p=0.332; hyper 240±5 vs. 244±10min; p>0.05). During recovery time before sleep T1pro displayed similar mean IG to CON (6.4±2.8 vs. 6.6±0.9 vs. mmol.l-1; p=0.553), which was significantly less than T1rec (9.3±1.7 mmol.l-1; p=0.013). Similar patterns were observed during sleep, whereby T1pro displayed similar mean IG to CON (T1pro 6.7±3.4, CON 6.1±0.9 mmol.l-1; p=0.412), which were both significantly less than T1rec (8.7±2.6 mmol.l-1; p<0.05). However, more T1rec individuals experienced nocturnal hypoglycaemia compared to T1pro (T1rec 66% vs. T1pro 13% patients) with more time spent hypoglycaemic (T1rec 402±62, T1pro 223±51 minutes; p=0.018) and lower mean IG nadir under T1rec (T1rec 2.6±1.3, T1pro 4.3±2.5, CON 4.4±0.7 mmol.l-1; p<0.05) during this time.

Conclusion: Recreational cyclists with T1DM had higher IG levels during exercise, in recovery and during sleep, and experienced more hypoglycaemic events than elite athletes with T1DM. Elite athletes with T1DM displayed IG comparable to people without diabetes during exercise, in recovery and during sleep. Glycaemic stability in elite athletes with T1DM provides a valuable insight to strategies that can be used to optimise glycaemic control during exercise in the wider T1DM patient population.